When University of Missouri defensive end Michael Sam announced Sunday that he is gay, the reaction was instantaneous and almost universally positive.

Several of Sam’s teammates tweeted their support. So did his school. A number of NFL players did, too, including Super Bowl MVP Malcolm Smith. The head of the NFL Players Association predicted Sam would be accepted “with open arms.” If drafted, he’ll be the first openly gay player in NFL history.

Even Michelle Obama offered encouragement. “You’re an inspiration to all of us,” she tweeted. “We couldn’t be prouder of your courage both on and off the field.”

There was one glaring exception: Sam’s potential future employers. As the Southeastern Conference’s Defensive Player of the Year last year, Sam is regarded by draft experts as anywhere from a third-round to a sixth-round pick in May’s NFL draft. But an article in Sports Illustrated Sunday was riddled with anonymous quotes from NFL coaches, scouts, and general managers all but promising that teams will discriminate against Sam because of his sexual orientation.

“It’d chemically imbalance an NFL locker room,” said one executive. “This is going to drop him down in the draft,” said another.

“If you knowingly bring someone in there with that sexual orientation,” complained one coach, “how are the other guys going to deal with it?”

Sam’s case is an explicit reminder that despite rapidly advancing cultural acceptance of gays and lesbians, workplace bigotry endures. But his unusual status as a gay pro football prospect means it’s an open question whether this sort of discrimination would be legal: Sam essentially has no say in where he’ll work, since whichever team drafts him will have exclusive rights to his services.

No federal law prevents employers from discriminating against him on the basis of his sexuality. So he’s uniquely exposed to the vagaries of state laws — or, in many cases, the lack of one.

If Sam winds up with, say, the New England Patriots, he’ll be protected by the laws that prohibit workplace discrimination in Massachusetts and 20 other states. But if he’s drafted by the Atlanta Falcons, he won’t be, since Georgia does not ban discrimination.

“Where you live determines whether you’re protected,” said Katherine Grainger, a former assistant counsel for civil rights under New York Gov. Andrew Cuomo.

Sam’s predicament illuminates an issue that’s been simmering on Washington’s back burner. For years, Democrats and some Republicans have been pushing for a federal Employment Non-Discrimination Act to prevent employers from firing, refusing to hire, or discriminating against applicants or employees on the basis of sexual orientation.

Such protections already exist for race, religion, gender, age, and disability. In November, the Senate passed ENDA by a vote of 64-32, with 10 Republicans joining the Democrats. But Republican Speaker John Boehner refused to introduce a bill in the House. “The speaker believes this legislation will increase frivolous litigation and cost American jobs, especially small business jobs,” his spokesman said.

Recent polls show that at least 70 percent of Americans believe gays and lesbians face “a lot” or “some” discrimination in the workplace (Pew Research Center), and a similar percentage supports laws protecting against job discrimination (Public Religion Research Institute). In fact, activists say one hurdle to passing ENDA is that many people assume such a law is already on the books.

Sam could end up reminding them otherwise. A Pew Research study last June found that lesbian, gay, bisexual, and transgender adults consider professional sports leagues overwhelmingly “unfriendly” toward them (the only organization rated more unfriendly was the Republican Party). Even if he doesn’t encounter discrimination, he could bring attention to the people who do and brighten the prospects for ENDA.

Not everyone agrees. “Michael Sam coming out is a wonderful thing and will accelerate the trend in public opinion,” says former U.S. Rep. Barney Frank, who introduced ENDA legislation while in Congress. “But it won’t have any near-term effect on Congress. Passing is going to take a Democratic House, Senate, and president or a transformation in the Republican Party that I don’t see happening.”

But Republicans aren’t the only impediment. Last week, Senate Majority Leader Harry Reid encouraged President Obama to sign an executive order extending federal protection to 16 million government workers and contractors. So far, he hasn’t.

Doing so wouldn’t affect Sam, even though the federal government grants the NFL tax-exempt status. But it would represent an important advance to go along with the big one that Michael Sam delivered Sunday.